I think the idea that you have to weep for your sins to be forgiven to be one, as well as the idea that you have to be able to sense the Holy Spirit in you to be a true Christian/truly saved.
I've kind of heard the first one alluded to. The second one sounds more Protestant - is it that common from your experience?
I don't know, I haven't heard it often, but I have a few places. I think I first encountered it in the writings of St. Symeon the New Theologian.
I thought most considered that a heresy? (I don't know much about it, I'm just going on what I've read others say)